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Arterial supply to brain:Middle cerebral artery (MCA), segments
The middle cerebral artery (MCA) is one of the three major paired arteries that supply blood to the brain. The MCA arises from the internal carotid artery (ICA) as the largest branch and continues into the lateral sulcus where it branches and supply the lateral aspect of cerebral cortex. Segments The MCA is divided into M1, M2, M3 and M4 segments: * M1 (horizontal): from the origin to bifurcation/trifurcation (the limen insulae). It is called sphenoidal segment as it tracks along the sphenoid bone. The M1 segment course laterally to the sylvian fissure below the anterior perforated substance before bi/trifurcating. Perforating arteries arise from M1 (lateral lenticulostriate arteries etc), which supply the basal ganglia. * M2: insular segment, from bi(tri)furcation from the M1, course within lateral cerebral fissure, over insula * M3: opercular segment (those within the Sylvian fissure) begin at top of insula, turn laterally in sylvian fissure to reach overhanging frontal/parietal/temporal operculae * M4: branches emerging from the Sylvian fissure onto the convex surface of the hemisphere; also known as cortical segment Branches M1 * lateral lenticulostriate penetrating arteries: these pass through the anterior perforated substance and supply the internal capsule, thalamus and basal nuclei. * anterior temporal artery * polar temporal artery: extends from the sphenoidal segment of the MCA via the operculum inferior surface and supplies the polar and anterior lateral portions of the temporal lobe. * uncal artery M2 Division of the MCA is variable after the horizontal segment, although most commonly, it divides into two trunks-superior and inferior: * 78% bifurcate into superior and inferior divisions * 12% trifucate into superior, middle and inferior divisions * 10% branch into many smaller branches Superior terminal branch: Supplies frontal lobe. * Lateral frontobasal (orbitiofrontal): This branches out to vascularize the inferior frontal gyrus. * Prefrontal arteries: fan out over the insula and exit to the cortex via the medial surface of the frontal operculum and vascularizes the inferior and middle frontal gyrus. * Pre-Rolandic artery (precentral): extends out on the medial surface of the operculum and supplies the middle and inferior frontal gyri as well as the pre-central gyrus. * Rolandic arteries (central): extends out and exits from the central portion of the operculum then passes inside the central sulcus to irrigate the pre-central gyrus and the post-central gyrus. Inferior terminal branch: supplies parietal lobe and temporal lobe * three temporal branches (anterior, middle, posterior): cross the superior and middle temporal gyri and supplies the temporal lobe * branch to the angular gyrus: pass over the anterior transverse temporal gyrus and supply the angular and supramarginal gyrus. * two parietal branches (anterior, posterior): ''runs along the spuramarginal gyrus and supplies the parietal lobe * ''Temporaloccipital: The longest cortical artery, it run posteriorly and exit from the Sylvian fissure, it run parallel to the superior temporal sulcus and supplies the superior and inferior occipital gyri. Vascular Territory: * The bulk of the lateral surface of the hemisphere; except for the superior inch of the frontal and parietal lobe (anterior cerebral artery), and the inferior part of the temporal lobe. * Superior division supplies lateroinferior frontal lobe (location of Broca's area i.e. language expression) * Inferior division supplies lateral temporal lobe (location of Wernicke's area i.e. language comprehension) * Deep branches supply the basal ganglia as well as the internal capsule Normal variants * MCA duplication-reported incidence of ~1.5% (range 0.2-2.9%); parallels the main MCA and supplies the anterior lobe * accessory MCA which arise as a branch from the ACA and runs parallel with the M1 segment. * MCA fenestration is rare with a report incidence of <1% * early branching of the MCA-bi/trifurcation (50 and 25% respectively) occurs within 1 cm of origin